<template>
    <div class="child">
      <h3>我是Child组件</h3>
      {{sum}}
    </div>
</template>

<script>
import { ref } from 'vue';

  export default {
    name:'Child',
    setup(){
      let sum = ref(0)
      return new Promise((resolve,reject)=>{
        setTimeout(()=>{
          resolve({sum})
        },1000)
      })
    }
  }
</script>

<style>
  .child{
    background-color: skyblue;
    padding: 10px;
  }
</style>